Hemoglobin Digestion

Introduction

Intraerythrocytic malaria parasites digest most of the hemoglobin of their host cells (Goldberg 2005; Rosenthal 2002). In a 70 kg person with a heavy Plasmodium falciparuminfection (20 % parasitemia), assuming 75 % degradation of hemoglobin within each infected erythrocyte, about one-third of a pound (~150 g) of hemoglobin is consumed in a single round of parasite growth. This, then, is an enormous catabolic effort. The purpose of hemoglobin degradation is not fully established. Parasites use some of the liberated amino acids for protein synthesis, and this utilization is increased when the exogenous amino acid supply is restricted. Indeed, cultures grown in the absence of most exogenous amino acids have near-normal proliferation (isoleucine supplementation is required, as human hemoglobin lacks this amino acid). In addition, a role for hemoglobin digestion in maintaining osmotic balance, perhaps even preventing premature rupture as the parasite grows, has been proposed....